The trend to miniaturized electronic devices has made appliance controls more vulnerable to electrostatic discharge (ESD) from human operators. Membrane switches increase the chances of damage since the thin membrane provides less isolation than traditional full-travel switches.
As the membrane keyboard is an interface between man & machine, there is a good chance that the static energy from human body will discharge while operating the keyboard. The body is charged with negative electrons. When these electrons come into contact with grounded conductive objects such as those found in membrane switches, they create a quick discharge of energy, or electrostatic discharge (ESD). This can cause damage to vital components and the machine may start malfunctioning. Even though electrostatic discharge cannot be prevented, effective shielding can help in protecting the devices. So it is essential to put EMI (Electromagnetic Interface) / ESD (Electrostatic Discharge) shielding for membrane keyboard used for sensitive machines such as medical instruments, military equipment, measuring instruments, balances, fuel dispensing machine etc. to protect them from interference or harmful frequencies. This shielding can be incorporated between the graphic and the upper circuit. This layer will help in cancellation or dissipation of electrostatic build up on a person’s finger.
Depending on the kind of membrane switch design, the graphic overlay material or the molded rubber materials both have a comparatively high dielectric strength and high volume resistivity. If required, a better degree of electrical shielding also can be integrated into the membrane switch construction. The requirements vary depending on the product and the industry it will be used in.
